But iOS app sales still outpace Android app sales 4 to 1

When it comes to which mobile application store to support, developers can factor in that Apple's App Store has the edge in volume, but Google Play -- the combined Android and HTML5 app store -- is on a growth spurt. Revenues from apps sold in the Google Play grew 17.9 percent in October compared to the previous month, while iOS App store sales shrink 0.7 percent in the same period. Compared to a year earlier, Google Play revenues grew 313 percent. iOS App Store revenues in October 2012 were 12.9 percent higher than in January 2012.

But iOS App Store revenues still were four times larger than Google Play's, according to the App Annie Index released today. The index ranks app stores by monthly downloads and revenues, segmented by stores, countries publishers and applications, with data based off market estimates from App Annie Intelligence data. App Annie declined InfoWorld's request for specific app store revenue numbers, saying that such information is part of its paid service.

"The gap between global revenues on iOS and Google Play is still there," said Bertrand Schmitt, CEO of App Annie. "But the gap is shrinking every month, creating more opportunities for publishers to generate significant revenue growth on Google Play in certain regions." Google Play features digital content for Android and Web systems along with some content for HTML5 and even iOS.

When examining free downloads, App Annie found that Google Play lagged slightly behind iOS, with nine downloads of Google Play apps for every 10 iOS apps downloaded. But Google Play's free-download numbers grew 47 percent in the last five months while iOS grew just 4.5 percent.

The index also showed that Japan overtook the United States in Google Play revenue in October. Globally, the United States had accounted for 33 percent of global iOS downloads at the beginning of the year but slipped to 25.3 percent in October.

App Annie also determined that several app publishers are making more money from one or two applications than some multinational publishers earn from more than 50. Supercell, NextFloor, Kabam, and WeMade Entertainment make money from users at an "astounding rate" from a small handful of applications, App Annie reported.

In terms of revenues, the top iOS publishers last month were Electronic Arts, Supercell, and Zynga. For Google Play, the top earners were DeNA, Colopl, and GungHoOnlineEntertainment. All six top revenue-generating publishers are games builders.

The top publishers by download numbers for iOS for October were Apple, Google, and Electronic Arts. For Google Play, the top publishers by downloads last month were Google, Facebook, and Rovio.

The index ranks app stores by monthly downloads and revenues, segmented by stores, countries publishers and applications, with data based off market estimates from App Annie Intelligence data